The proposed research concerns the chemical synthesis and biological evaluation of new vitamin D3 (cholecalciferol, D3) analogs and metabolites. Chemical development studies include: (a) the vinylallene method for constructing the l-hydroxyvitamin D system; (b) the total synthesis of 1 alpha, 25-dihydroxyvitamin D3 (1 alpha, 25-(OH)2-D3); (c) fundamental studies of vinylallene chemistry ((1,5)-sigmatropic shifts, chiral metallo-allenes, dienallenes and cyclopropylallenes); (d) mechanism of (1,7)-sigmatropic shifts; (e) reduction, oxidation and photochemical reactions of D3, 25-hydroxy-vitamin D3 (25-OH-D3) and 1 alpha, 25-(OH)2-D3. Using the vinylallene or other methods, we plan to synthesize a number of analogs and metabolites which may be useful for our understanding the mode of action of vitamin D at the molecular level in its endocrine system. Synthetic targets include: (a) A-ring, side chain, C/D ring and triene modified analogs of 1 alpha 25-(OH)2-D3, 25-OH-D3, and D3; (b) metabolites and/or catabolites. These analogs, which can be classified as agonists, antagonists or synergists, are of importance for determining the structural, stereochemical and conformation requirements necessary for optimal or minimal in vitro receptor binding and in vivo biological activity. The synthetic agonists will be evaluated in vitro in the chick intestinal receptor and putative bone receptor assay systems and studies will be made to correlate the results with in vivo intestinal calcium absorption and bone calcium mobilization data. Attempts to identify antagonists, particularly an anti-l alpha, 25-(OH)2-D3 factor with possible application in the treatment of cancer, and synergists will continue. The structural elucidation and synthesis of recently discovered as well as putative new metabolites will be attempted. Analogs related to 10,19-dihydrovitamins will be further examined for their possible application in the preparation of affinity chromatography systems and for developing a radio-immunoassay for D-metabolites. Mass spectral and other spectroscopic studies of vitamin D steroids will continue. Stereostructural and biological studies of the macrolide antibiotic filipin will be initiated.